[PATCH 6.9 288/374] dma-mapping: benchmark: fix up kthread-related error handling

Greg Kroah-Hartman
2024-06-06T14:10:49Z

From: Fedor Pchelkin <pchelkin@ispras.ru>

[ Upstream commit bb9025f4432f8c158322cf2c04c2b492f23eb511 ]

kthread creation failure is invalidly handled inside do_map_benchmark().
The put_task_struct() calls on the error path are supposed to balance the
get_task_struct() calls which only happen after all the kthreads are
successfully created. Rollback using kthread_stop() for already created
kthreads in case of such failure.

In normal situation call kthread_stop_put() to gracefully stop kthreads
and put their task refcounts. This should be done for all started
kthreads.

Found by Linux Verification Center (linuxtesting.org).

Fixes: 65789daa8087 ("dma-mapping: add benchmark support for streaming DMA APIs")
Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/dma/map_benchmark.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/kernel/dma/map_benchmark.c b/kernel/dma/map_benchmark.c
index 02205ab53b7e9..2478957cf9f83 100644
--- a/kernel/dma/map_benchmark.c
+++ b/kernel/dma/map_benchmark.c
@@ -118,6 +118,8 @@ static int do_map_benchmark(struct map_benchmark_data *map)
if (IS_ERR(tsk[i])) {
pr_err("create dma_map thread failed\n");
ret = PTR_ERR(tsk[i]);
+ while (--i >= 0)
+ kthread_stop(tsk[i]);
goto out;
}

@@ -139,13 +141,17 @@ static int do_map_benchmark(struct map_benchmark_data *map)

msleep_interruptible(map->bparam.seconds * 1000);

- /* wait for the completion of benchmark threads */
+ /* wait for the completion of all started benchmark threads */
for (i = 0; i < threads; i++) {
- ret = kthread_stop(tsk[i]);
- if (ret)
- goto out;
+ int kthread_ret = kthread_stop_put(tsk[i]);
+
+ if (kthread_ret)
+ ret = kthread_ret;
}

+ if (ret)
+ goto out;
+
loops = atomic64_read(&map->loops);
if (likely(loops > 0)) {
u64 map_variance, unmap_variance;
@@ -170,8 +176,6 @@ static int do_map_benchmark(struct map_benchmark_data *map)
}

out:
- for (i = 0; i < threads; i++)
- put_task_struct(tsk[i]);
put_device(map->dev);
kfree(tsk);
return ret;
--
2.43.0